Have not read the book, but to have a planned economy, you need planners. Planners are human and no matter how good, they will eventually make a big mistake.
I fear that this is happening to the US to some degree where the planners are basically, fannie mae, freddie mac, the big banks and hedge funds. Risk has be socialized and diffussed throughout US society, that we may be headed for a blow up.
von Mises central thesis is that planners cannot plan the price mechanism, therefore there's no way to efficiently allocate resources to their best use, best meaning what is in demand.
It is because of the lack of a free price mechanism that a socialist economy fails.
If you read only one book in economic principles, this should be it.
The influences today ? Federal Reserve, EPA, OSHA, NEA, and the massive books of federal and state regulations and taxes that are choking business activity.